DE2533357A1 - AZEOTROPIC COMPOSITION - Google Patents

Description

The invention relates to azeotrope-like compositions of matter.

The azeotrope-like compositions of matter according to the invention are excellent solvents for removing flux in the electronic technology used circuit boards. Such circuit boards usually consist of a glass fiber reinforced one Carrier body made of electrically resistant plastic with electrical connection elements provided on one side. The connection elements are thin, flat strips of conductive metal, usually copper, that serve to hold the on the other side of the circuit board to connect electronic components to each other. The electric The integrity of the contacts between the connection elements and the components is ensured by soldering.

In today's technical processes for soldering circuit boards there is a covering of the entire circuit side of the

509886/0932

253335?

OR-5571

Plate with a flux and then passing the coated Plate side by molten solder. The flux cleans the conductive metal parts and promotes adhesion of the plumb bob. The preferred fluxes consist for the most part of rosin, used alone or together is used with activating additives, such as an amine hydrochloride, Trimethylamine hydrochloride or oxalic acid derivative.

After soldering - which thermally degrades part of the rosin or decomposed - the flux is removed from the plate using an organic solvent. Lots of for Solvents recommended for this purpose attack the organic materials from which circuit boards are often made and other solvents are undesirable because of their level of flammability and toxicity.

A solvent recommended for cleaning circuit boards is 1,1,2-trichloro ~ 1,2,2 ~ trifluoroethane, which is non-flammable, is not very toxic and non-aggressive. To increase the flux dissolving power of trichlorofluoroethane has been recommended to mix more active solvents with it. To activate Solvents include lower alcohols, such as methanol, which, however, are reactive in combination with trichlorotrifluoroethane Metals such as zinc and aluminum as well as certain aluminum alloys and chromate coatings used in circuit board assemblies Can find use, can attack (in an undesirable way). Methanol is the most aggressive in this regard common alcohols and is not used in contact with these metals.

The solvent compositions according to the invention have the advantages of trichlorotrifluoroethane / methanol combinations, but without the above-mentioned disadvantage of aggressiveness to have the reactive metals. The compositions of matter according to the invention are for use with even more reactive ones Metals such as alkaline earth and alkali metals are not suitable. These metals are typically not found on printed circuit boards.

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509866/0932

25333b?

OR-5571 -

The use of nitromethane to prevent metal attack by trichlorotrifluoroethane mixtures with other alcohols known. It is known to use these mixtures for flux removal of circuit boards to use. These mixtures cannot be used in boiling »by the cleaner and economy are far better because the solvent changes its composition when used may be subject to. The compositions of matter according to of the invention, however, are suitable for use in boiling and give good metal protection throughout their life of the solvent.

The azeotrope-like compositions of matter according to the invention contain 5.0 to 6.3% by weight of methanol, 0.05 to 0.6% by weight of nitromethane and 93.1 to 94.95% by weight 1,1,2-IrIChIOr-1 ^, 2-trifluoroethane. The particularly preferred compositions of matter according to the invention contain 5.5 to 5 »9% methanol and 0.1 to 0.3% nitromethane, the remainder trichlorotrifluorathane, in each case based on weight.

The compositions of matter according to the invention are considered to be "azeotrope-like" referred to because they behave like azeotropes under operating conditions as described in the examples, i.e. H. the composition of the vapor formed during boiling or evaporation is with the composition of the original Liquid almost identical. During boiling or evaporation, as in the case of the use described later, changes to a vapor degreaser, the liquid composition only minimal. In contrast, show non-azeotropic compositions of matter increasingly different solvent compositions due to the distillation process and evaporation loss, accompanied by the loss of at least one component and its beneficial effects.

The new compositions of matter according to the invention are further characterized by non-flammability in air under all conditions from, while compositions of matter, the larger people

509886/0 9 32

genes of methanol or Mtromethane contain during evaporation become flammable. In addition, the solvents according to the invention inhibit the attack on active metals that normally occurs in anaerobic conditions such as those in a vapor degreaser occurring, would occur. This result is in contrast to combinations of methanol and halogenated hydrocarbons without nitromethane. Surprisingly, this benefit is achieved without compromising flux removal ability the azeotrope-like compositions of matter obtained.

To produce the compositions of matter according to the invention, the individual constituents are mixed in the proportions mentioned. Every component is commercially available in a high degree of purity. While a presence of the ingredients in high When purity is preferred, incidental impurities will affect the behavior of the azeotrope-like compositions usually not adversely affect.

A vapor degreaser is usually used to apply the solvent compositions according to the invention to the circuit boards to be cleaned of rosin-based flux or use steam degreasing equipment. In the conventional operation of a steam degreaser, the plate is through a "Sump" or stock of boiling solvent, which removes the bulk of the rosin, then through a "Swamp", which contains freshly distilled solvent near room temperature, and finally through solvent vapors above the boiling sump, resulting in a final rinse with pure, clean solvent that condenses on the circuit board results. In addition, the plate can also be sprayed or sprayed with distilled solvent before the final rinse. -be sprayed.

The present azeotrope-like compositions of matter are found to be resistant to changes in methanol concentration very sensitive. Any deviation in the alcohol concentration outside the range from 5 »0 to 6.3% leads to

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Settlements which are subject to a pronounced change in composition during boiling or evaporation. Against changes the nitromethane concentration on the other hand are the Substance compositions relatively insensitive. It can go up 0.6% by weight of nitromethane without loss of the azeotrope-like character the composition of matter.

There is evidence that a true azeotrope exists which is approximately 6.1 wt% methanol, 0.01 wt% nitromethane, balance (about 93.89%) 1,1,2-trichloro-i, 2,2-trifluoroethane contains. During this true azeotrope, a satisfactory solvent remover solver represents, like the binary azeotrope of methanol and 1,1,2 ~ trichloro-1,2,2-trifluoroethane, it takes some active metals. The compositions of matter must be how has been shown to contain at least 0.05% by weight of nitromethane to avoid this attack.

The following examples serve to further illustrate the invention.

Examples 1 and 2 " and comparative experiments

This example illustrates the azeotrope-like behavior of the compositions of matter according to the invention in contrast to FIG the compositions of matter outside the scope of the invention.

The ternary compositions of matter mentioned in Table I were used prepared and placed in small double sump laboratory degreaser, the sumps of 10.16 χ 17.78 χ 17.] 78 cm Depth (about 3210 cm / sump). In the beginning, feathers became a swamp immediately after entering the composition of the material a 30 cm sample is taken in the swamps for analysis. Then the degreaser was started and refluxed for 8 hours left, after 1, 4 and 8 hours of reflux, 30 cm samples were taken from each sump.

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OR-5571

All samples were analyzed by calibration vapor phase chromatography. The degreaser was made of flat, flat plastic material covered to avoid loss of vapors due to drafts and convection currents to minimize. The solvent losses ranged from 1.25 to 8.7% of the initial bottom volume. Heat was supplied to the boiling sumps in such a way that the rinsing sump was converted 2.0 to 2.2 times per hour. Related to a vapor / air interface of 4A5> 94 cm was the average Solvent loss rate about 0.015

ρ
up to 0.12 g per hour per cm. The results are given in Table I together with comparative experiments A to I outside the scope of the invention.

509886/0932

Tabel!

Example (number) component
or comparison test {letter)

Methanol
Nitromethane

Methanol
Nitromethane

2 3 3

Methanol

Nitromethane

Methanol
Nitromethane

Methanol

Nitromethane

0 ^. 01,

Methanol
Nitromethane

Analyzed composition, wt.%, Of collected samples

during 8-door operation

Boiling sump test ^ j Spulsumpxprobe *

94.52 94.55 94.70

5.28 5.25 5.10

0.20 0.20 0.20

93.70 93.66 93.56

6.10 6.14 6.23

0.20 0.20 0.21

95.40 95.90 96.14

4.13 3.64 5.41

0.47 0.46 0.45

95.43 95.90 96.14

4.07 3.60 3.35

0.50 0.50 0.51

91.36 89.49 88.88

8.26 10.06 10.64. ·

0.38 0.45 0.48

94.76 94.92 95.31

5.05 4.88 4.49

0.19 0.20 0.20

94.74 94.76 94.41 94.47 94.23 5.06 5.05 5.40 5.34 5.58 0.20 0.19 0.19 0.19 0.19 93.52 93.72 93.78 93.84 93 »84 6.27 6.08 6.03 5.97 5.9? 0.21 0.20 0.19 0.19 96.67 95.49 94.04 94.04 2.83 4.11 5.52 5.51 0.45 0.40 0.44 O ₅ 45 96.28 95.43 94.01 93.95 3.21 4.07 5.52 5.57 5.5C 0.51 0.50 0.47 0.48 0.49 88.59 91.55 93.08 93 ₅ 45 c) 3 _v 49 10.92 8.08 6.59 a ">: /. 0., 20 0.49 0.37 0.33 0.52 0.31 95.56 94.75 94.05 94.20 94.0.5 4.24 5.05 5.61 5.70 0.20 0.20 0.18 0.19 0.19

■■■! · *

Table I - (continued)

cn O CD OO OO CD

Example (number) component or comparison test (letter)

Methanol nitromethane

C ₂ F ₅ Cl ₃

Methanol

Nitromethane

Methanol nitromethane

C ₂ F ₅ Cl ₃

Methanol nitromethane

O ₂ F ₅ Ol ₅

Methanol nitromethane

Composition analyzed, wt%, during 8 hours of operation collected samples

Boiling sump fprobe *) ABCD sump sample *)

92.76 91.86 91.75 7.02 7.87 8.00 0.22 0.27 0.27

89.09 82.54 79.62 -

10.71 17.37 20.03 -

0.20 0.29 0.35 -

89.4-9 85.77 83.66 83.01

10.32 13.98 16.07 16.71

0.19 0.25 0.27 0.28

86.78 80.14 76.31 74.83

13.03 19.58 23.36 24.83

0.19 0.28 0.33 0.34

91,878 90,778 89,703 89,574 8.104 9.198 10.275 10.403 0.018 0.024 0.022 0.023

*) A »After loading, before operating the device B * after 1 hour of operation C «after 4 hours of operation D ■ after 8 hours of operation

92.77 93.53 93.57 -

7.01 6.27 6.23 0.22 0.20 0.20

88.98 92.88 93.21 10.82 6.97 6.64 0.20 0.15 0.15

89.48 92.38 93.32 93.38

10.33 7-6 6.54 6.48

0.19 0.16 0.14 0.14

86.79 91.67 92.95 92.96

13.02 8.19 6.93 6.92

0.19 0.14 0.12 0.12

91,867 93,468 93,764 93,759

8.115 6.515 6.221 6.224

0.018 0.017 0.015 0.017

CO U) CO

· 9 ·

Examples 5 Ms 8 and comparative tests

These examples show the influence of mtromethane on the Stability of the compositions of matter according to the invention in the presence of various metals under anaerobic conditions.

5 ml samples of the compositions of matter and metals according to Table II were placed in glass vials with an internal diameter of 1.59 cm and a length of 6.35 cm which had screw caps lined with polytetrafluoroethylene. The aluminum samples used here had a size of 6.03 χ 0 _t 635 x 0.159 cm and the sheet metal samples made of galvanized steel were 6.03 x 0.635 x 0.079 cm. The aluminum alloy had a 120 grit surface while the galvanized material was used as it is. The closed small bottles were placed in a bath with a temperature equal to the boiling point of the solvent and vented after 5 minutes at the boiling point by opening. The test vials were left in the bath for 24 or 48 hours to be cooled and examined. The results are shown in Table II.

In the table, the percentage of decomposition is based on the amount of Cl "found in the test system and the theoretical amount of Cl" that could be formed if 100% of the GFgClGFClg solvent were decomposed; "Ml" means a decomposition equivalent to 0.007% or less, "VP" in contact with the vapor phase and ¹¹ LP "in contact with the liquid phase.

+) ground with abrasive grain, the largest dimension of which was 120 microns.

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Table II

composition example Test metal Galvanized
stole ■ Check Decomposed Changes in appearance of the metal _{or similar}
ψ
VJi
VJi of the test solution
by means of
CF ^ ClCFClp / methane
ol / nitromethane,
Weight% (Number)
or Ver
equal
attempt
(A book
stick) m _ It _ Time,
Hours. tongue,% the liquid VP: De-zincified, 100 %.
LP: de-zincified / mat
animal, 50% / 50%. 93.86 / 6.14 / 0 J - "- 24 0.97 Very minor, white ones
Precipitation; Present
two liquid phases. as before 93.85 / 6.14 / 0.01 K 24 ■ 0.96 as before no 93.81 / 6.14 / 0.05 3 _ "- 24 NILE no no cn
ο 93.76 / 6.14 / 0.1 4th Al-Legie
tion **) 24 0.07 no no co
on 93.56 / 6.14 / 0.3 5 _ ti _ 24 0.07 no VP: Massive storage
white gel,
100%.
LP: lightly etched /
light deposit
colorless gels,
100% / 50%. 186/0932 93.86 / 6.14 / 0 L. 48 0.37 no no 93.85 / 6.14 / 0.01 M. - "~ 48 NILE no no 93.81 / 6.14 / 0.05 6th 48 NILE no no 93.76 / 6.14 / 0.1 7th 48 NILE no no 93.56 / 6.14 / 0.3 8th 48 NILE no

**) AL-1100 = commercial grade aluminum

(Degree of purity 99 % or higher)

Examples 9 to 12 and comparative experiments

These examples illustrate the detergency of compositions of matter according to the invention when used with soldered electronic circuit boards.

The plates had a uniform circuit pattern on one side of an epoxy resin glass fiber base 3.49 x3.18 cm in size. The plates were provided with ten through-holes as a means of mounting components. Four holes were connected with two tinned wires bent on the circuit side to mimic mounted components. ^{For E 1} solvent treatment, these plates were placed with the circuit side in a mass of highly activated commercial flux. To harden the flux, the flux-treated, downward-facing side was placed on a clean aluminum surface on a steam plate for 2 minutes. The plates were then applied for soldering with the flux-treated surface 5 »0 + °» 2 seconds on the surface of 50/50 Pb / Sn solder at 258.8 to 243.3 ° C, from which the solder skin had been removed . Then the pieces were cooled and subjected to flux removal within one hour after soldering.

To remove the flux, the diagonally opposite The corners of the plates held with tweezers are dipped in the boiling solvent for 4 minutes, which is in a small stainless steel degreaser. The plate was then pulled up into the steam zone for 15 seconds rinsed with the pure solvent (in the form of condensate from the boiling solvent) and then before the Pull out and leave in steam for 15 to 30 seconds. the The conductivity test in the aqueous medium was carried out (as described below) immediately after the flux was removed.

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509886/0932

The measurement of the conductivity in the aqueous medium was carried out as follows: In a measuring cylinder with a polytetrafluoroethylene-coated Magnetic stirrer contained was a

ρ
100 ml per 32.5 cm plate surface are given the corresponding volume of deionized water. The aqueous conductivity of the deionized water was measured to a hundredth of a microSiemens / cm with a conductivity standard cell of the Beckman type, which was connected to a conductivity bridge ^. For this purpose, the plate subjected to the flux removal was immersed in the purified water, the magnetic stirrer was put into operation and the increase in conductivity of the aqueous medium was recorded for up to two minutes at intervals of half a minute. The recommended limit value recognized for acceptable cleaning of electroplated parts is a maximum increase in the conductivity of the aqueous medium of 1.0 microsiemens / cm.

For each test reported here, at least three separate determinations were made; the results were averaged and rounded up or down to the nearest tenth microsiemens / cm. For measured values below the 1.0 microSiemens / cm value the separate readings agreed to +0.04 microsiemens / cm and the higher readings agreed + 0.07 microSiemens / cm.

The results given in Table III show that the compositions of matter result in acceptable cleaning of printed circuit boards according to the invention. It should be mentioned that if any nitromethane is left on the plates after flux removal, it will be used for conductivity could contribute; any such effect does not appear to be significant in the present results.

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509886/0932

T a b le 1 e III

O CD OO 00 OO

Example (number) / comparison experiment (letter)

10 11 12

VN I

Flux remover solvent, wt.%

GF ₂ ClCFCl ₂ CH-, ΟΉ
3 CH ₅ NO ₂ 93.6 5.9 0.5 93.2 6.3 0.5 93.9 5.9 0.2 93.9 5.9 0.2 94.1 5.9 0 93.7 6.3 0 93.7 5.9 0

distance
all flow
by means of Average conductivity
increase,
Microsiemens / cm ?
VJi Yes 0.9 Il 0.9 ti
Il 0.5 π 0.8 It 0.7 It

Example 13

This example shows a simulation of a 10-day operation in a three-sump degreaser.

A three-sump vapor degreaser, the composed of boiling sump, rinsing sump and spray sump. To simulate the operating conditions during the 10 days Two endless chains made of brass chain of the type used for adjustable windows (chain length in each case 2.13 m; 1.14 links / cm; 1.5875 mm wire) continuously under Motor drive via a driven roller and moving rollers guided through the following positions: 1. Air space above the Degreaser and in the degreaser, 2nd solvent vapor, 3rd boiling solvent, 4th solvent vapor, 5 rinsing sump solvents, 6. Solvent vapor and 7 · air space in and above the degreaser. During the first 24 hours the chain became not run.

Vapors from the boiling sump were condensed and returned to the spray sump. Overflow from the spray sump became the rinsing sump and overflow from the latter led to the sump.

The sumps had the following dimensions and loads: Boiling sump 30.48 30.48 χ 29.21 cm or 50.42 kg; Rinsing sump 25.4 χ 30.48 χ 36.83 cm or 49.00 kg and spray sump 17.78 χ 30.48 χ 22.56 cm or 18.14 kg. The vapor area of the degreaser open to the atmosphere only comprised the area above the boiling and rinsing sumps and was 1700 cm ² (30.48 × 55.88 cm). The steam loss ratio was 0.83 (25.4: 30.48 cm). The heat input to the sump (1548.4 kcal / hour) and the estimated heat of vaporization of 48.99 cal / g solvent resulted in flush sump and spray sump conversions of 0.7 to 1.8 times per hour.

Immediately after loading the three sumps, while the liquid was still at room temperature, and according to the time program According to Table IV, samples of the liquid materials were made

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the boiling and rinsing sumps for gas chromatographic analysis taken. Supplementary samples were also taken from the spray sump at a later point in time. The rate of solvent loss does not include the amount of solvent withdrawn for analyzes. Before taking the 31 ml samples the temperatures of the liquid in the sump with the boiling solvent were measured and corrected to 760 mm pressure. After taking the samples, the liquid level was brought to the original maximum level (100% filling), to enable a more precise calculation of the speed of loss. At other times the sump became automatic refilled to 100% when the fluid level dropped to 90%. The fresh refill solvent was used gravity fed from a tarred 18.93-1 drum hopper introduced into the bottom of the flushing sump. The rate of solvent loss was during first 24 hours and during the rest of the test time

0.5 or an average of 2.2 kg per hour per m.

The results of the analyzes of the liquid samples taken from the three sumps are summarized in Table IV. In connection with the temperature calculations it should be mentioned that the temperature display of the thermistor used in the present study was also corrected against a mercury thermometer that was calibrated _{in the condensing vapor of CpF 7} -Cl _{71 in an ebullioscope.} All values have been subtracted from 0.1 ° C (the actual correction was -0.08 ° C). The display division of the thermistor corresponded to 0.6 ° C. A division to about 0.2 ° C was carried out by interpolation.

The above steam loss ratio ("Freeboard Radio") represents the rate at which steam is lost; this ratio is equal to the distance between the surface of the steam jacket and the top of the device, divided by the width of the device.

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Table IV

oo co cn

Solvent refill ^ boiling sump

Time- Currently accumulated, temperature

%, of the original ( corrected to 760 mm ft, initial), low-sump feed ⁰ C methane-nitro-

Point,
Stun
the the Ge
weight
test,
kg mm » 0 0 ^b 4th - 24 2.268 48 9.825 72 9,652 96 8,464 168 21.52 192 - 216 10.13 240 8.165

Composition, wt%, of the ternary mixture of Example 13 (methanol and nitromethane concentrations

as folftt, Eest C gF-zCl ^

Spu ^ suMpf

1.9 10.3 18.5 25.7 44.0

52.6 59.6

39.7 39.8 39.8 40.0 40.0 39.8 39.7

39.8 39.9

oil

5.86

5.87 5.84 5.90 5.92

methane

5.93 ^a o, 49

5.92 0.53

5.82 0.55

Methanol

5.95
5.94

5.91
5.88

5.91
5.89
5.87

Kitromethane

0.49 0.43 0.44

0.45 0.45 0.45 0.45 0.45

Sp run dull

Methane-

oil

5.89 5.88 5.86

Nitromethane

(5.92) (0.49)

0.44 0.44 0.45

a »Analysis of room temperature solvents in the boiling and rinsing sumps immediately after filling all three sumps.

b β about 10 minutes after the solvent began to boil and the steam jacket formed. CO CO CO

Claims (5)

OE-5571 '% * ϊ * · Patent claims 1. Azeotrope-like composition with a content of 5.0 to 6.3% by weight of methanol, 0.05 to 0.6% by weight of nitromethane and 93.1 to 94.95% by weight of 1,1,2-trichloro-1,2,2-trifluoroethane. 2. A composition of matter according to claim 1 with a content of 5.5 to 5.9% by weight of methanol, 0.1 to 0, 3% by weight of hitromethane and 93.8 to 94, 4% by weight of 1,1,2-trichloro-1,2,2-trifluoroethane. - 17 - 5 09886/0932